Final answer:
The correct metric unit to calculate the distance from here to San Diego is kilometers (km), as it is used for measuring long distances.
Step-by-step explanation:
To calculate the distance from here to San Diego, you would use the metric unit of kilometers (km). This unit is appropriate because kilometers are used to measure long distances, such as the distance from one city to another. The options provided in the question were A. kg (kilograms), B. L (liters), C. mm (millimeters), and D. km (kilometers).
Kilograms are used for measuring mass, liters are used for volume, and millimeters are used for very small lengths, usually much smaller than what is needed to measure distances between cities. Therefore, km is the correct metric unit to calculate the distance from your location to San Diego.